Long-Term Follow-Up of Hyperthyroid Cats Treated with Iodine-131

A long-term follow-up study of hyperthymid cats treated with iodine-131 was conducted at the Texas A&M University Veterinary Teaching Hospital. Between January 1985 and December 1990, 255 cats were treated. Basic demographic data, information on treatment, and diseases at the time of diagnosis were recorded. Two hundered and thirty seven cats had long-term follow-up data collected by teiephone interviews with the referrting veterianan and/or owner on outcome of therapy, disease that developed during the follow-up period and survival. Risk for developing hyperthyroidism was highest for cats greater than 10 years of age. There was no breed predisposition. Neutered cars were siighfjy over-represented amoung the cases compared to intact animals. Eighty-five percent of treated cats became clinically normal and remained euthyroid tor a median time of 17.5 months. Four percent remained hyperthyroid and 9% became hypothyroid, requiring thyroid hormone supplementation